2000-2016年黄河源区植被NDVI变化趋势及影响因素

Change Trend of Vegetation NDVI and Its Influencing Factors in the Source Region of the Yellow River in the Period from 2000 to 2016

NDVI是研究区域植被变化的重要表征性指数。基于2000—2016年的MODIS NDVI遥感数据和同时期地面气象数据,采用非参数检验方法曼—肯德尔法(Mann-Kendall)检验法、斜率变化趋势分析法、复直线回归分析法等多种时间与空间分析方法,研究了黄河源区生长季植被覆盖时空变化及其与气候因子的相关性,探索黄河源区植被与气候变化的时空耦合关系,分析了气候因素及人类活动对植被覆盖的影响。结果表明:黄河源区NDVI在2000—2016年期间没有特别明显的突变年份;源区70.4%的区域植被NDVI是增加的,增长率大部分处于0～0.004/a。复直线回归分析显示气象因素对源区植被生长变化起到主要的促进作用,99%的区域NDVI气候因素贡献值为正值。人类活动促使植被NDVI增加的区域占总面积的比例是55%,说明人类活动等因素对黄河源区的生态环境产生一定的积极影响,但仍有接近50%的区域人类活动使NDVI减少,高寒草地的退化的趋势没有得到有效遏制。

NDVI is an important characteristic index of vegetation change. This study is based on the MODIS NDVI from 2000—2016 and the surface meteorological data at the same period. The spatial and temporal changes of vegetation cover in the growing season of the Yellow River and its correlation with climatic factors, the temporal and spatial coupling relationship between vegetation and climate change in the source region of the Yellow River and the impact of climatic factors and the human activities on vegetation cover were analyzed and explored by using non-parametric test methods such as Mann-Kendall analysis, trend analysis, and multi-linear regression analysis. The results showed that the NDVI of the source region of the Yellow River had no significant abrupt year from 2000 to 2016;the NDVI of the 70.4% of the source region increased, and the growth rate was mostly between 0~0.004 a. The meteorological factors played the major role in promoting the vegetation growth in the source region, and climatic factors contributed the positive values in 99% of the area. The proportion of areas where human activities played the positive role in NDVI increase was 55%, indicating that human activities and other factors had a certain positive impact on the ecological environment in the source region of the Yellow River, human activities had reduced NDVI in nearly 50% of regional, indicating that the trend of degraded alpine grassland had not been effectively curbed.